Method of inhibiting corrosion of metals



t and brines.

United States Patent No Drawing. Application May 17, 1954 t Serial No. 430,448 r 6 Claims. (01.252-855) METHOD OF This invention relates toinhibiting corrosion of metals and is more particularly concerned with improved compositions and processes for treating natural oil-brine mixtures to reduce their corrosive action upon production, transmission, and other oil field equipment.

It is a well-known fact that many oil producing formations yield with the crude oil a brine whichis extremely corrosive in its action upon metal tubing, casings, pumps and other oil producing and collection equipment; and that this type of corrosion is particularly noticeable in wells producing brines containing dissolved hydrogen sulfide, carbon. dioxide or other acidic materials. In the past, efiorts have been made to reduce the cost of maintaining production and collection equipment by introducing into the well caustic soda or other alkaline solutions in such proportion as to neutralize the acidic components, or by the use of certain water-soluble corrosion inhibiting agents such as formaldehyde, bone oil, nitrogen bases of various types, amines, and combinations of these reagents. While these corrosioninhibitors are satisfactory at a number of locations when used in wells which produce little water as compared to the oil produced, their cost becomes prohibitive when used in wells producinglarge amounts of water, since the same concentration of the inhibitor must be maintained in the water phase in both types of wells in order to" satisfactorily prevent corrosion of j the equipment.

products obtained by reacting, according to the method of Riebsomerfl. Org. Chem. 15, 241, 1950) two mols of a polyethylenearnineisuch as diethylene trial-nine, triethylene tetramine, or tetraethylene pentamine, with one mol of a dibasic acid having 8 or more carbon atoms,

are very efiective in lowering thecorrosive action of oil I have now discovered that if the products so prepared are reacted further with one or two mols of an aldehyde so as to introduce into the structure one t or more imidazolidine or imine group, dicarboxylic acids having less than 8 carbon atoms,wsuch as succinic acid,

may also be successfully used, the resultant compounds show surprisingly greater effectiveness in combatting corrosion, and afford substantial protection when present in the oil-brine mixture in amounts rnillion. v

My new corrosion inhibitor compositions fall into the class ofsubstituted bis-imidazolines having the gen- 'eric formula as low as five parts 'per onward iarnn R-N N N-R Ice 2,836,557

Patented May 27, 1958 in which Y is a hydrocarbon radical having more than 1 carbon atom, one R is in which R may be hydrogen or a hydrocarbon radical, and the other R is (4), (5), or (6).

The exact form which each R would take would depend on the polyethylene amine employed, and the number of mols of aldehyde reacted with the primary reaction product. Thus, if the amine used were triethylene tetramine, and the intermediate acid-amine reaction product were reacted with one mol of an aldehyde, one R would be (2) and the other R would be (5); if two mols of an aldehyde were used, both Rswould be (5).

Similarly, if the amine were diethylene triamine, and one mol of an aldehyde were used, time R would be (1), and the other would be (4); two mols of an aldehyde would yield a product in which both Rs were (4). If instead of using two mols of the same amine, a mixture of amines are used, structures having both an imine and an imidazolidine group may be obtained. For, example, if one mol of diethylene triamine and one mol of tetraethylene pentamine were reacted with one mol of a dibasic acid, and this intermediate product reacted with two mols of an aldehyde, a mixture of products would result, in some of which both Rs would be (6), in some of which both Rs would be (4), and in some of which one R would be (4) and the other would be (6).

The aldehyde employed would determine the structure of R. For example, if formaldehyde were used, R would be a hydrogen atom, if acetaldehyde were used, R would be CH and for higher aldehydes R would be a higher molecular weight hydrocarbon radical of one less carbon atom than the aldehyde used.

As an example of the method by which my compositions may be prepared the following example is given, it being understood, however, that the exact conditions given in the example are not in any Way critical.

EXAMPLE To a mixture of 30 grams (0.1 mol) of dimerized linoleic acid prepared according to the directions given in Journal of American Oil Chemists Society, 24, 65 (March 1947) and hereafter referred to as dimer acid, and 29.2 grams (0.2 mol) of diethylenetriamine, 50 ml. of benzene was added. The mixture was heated under a water-trap condenser in order to distill the waterbenzene azeotrope mixture, with the benzene being returned continuously through the decanter still'head to the reaction mixture. After a four-hour reaction period, 6.8 grams of water had been'collected, which was almost the theoretical quantity which would be split out by the reaction of the amine with both carboxyl groups of the dimerized acid to produce the bis-imidazoline. Six grams, or 0.2 mol of formaldehyde were then added,

3 and refluxing was continued until sufiicient water had been split out to indicate that the desired di-imine had been formed, after which the remaining benzene was distilled off.

In order to test the effectiveness of my new compounds in combatting corrosion, the following procedure was adopted. To a one liter Erlenmeyer flask 600 ml. of a 5% aqueous sodium chloride solution and 400 ml. of depolarized kerosene was added. A steel strip was then suspended in the liquid by means of a glass hook through a rubber stopper in such a manner that half of the strip was in contact with the kerosene, and the other half in contact with the aqueous layer. The stopper Was also equipped with a gas inlet and outlet line. Natural gas or nitrogen was then blown through the liquid for about one hour, in order to purge any oxygen present, and the inhibitor was added. Hydrogen sulfide was then blown through the liquid until it was saturated, and the flask was then sealed and allowed to stand 48 hours. The steel strip was then removed, cleaned, and Weighed to determine the weight loss due to corrosion. In all cases duplicate tests were run to determine the weight loss of strips subjected to the action of uninhibited liquids, and thus determine the effectiveness of the corrosion inhibitor.

The results of these test calculations are summarized in the following tables in which TETA is triethylene tetramine, DETA is diethylene triamine, and TEPA is tetraethylene pentamine. The first three columns indicate the reactants used, the fourth the molar proportions in which they were reacted, and the remaining colums the percent corrosion at various concentrations of inhibitor in the oil-brine mixture. Blanks indicate that the compositions were not tested at these concentrations. Percentage corrosion in all instances is the weight loss of the strip exposed to the inhibited liquid divided by the weight loss of a strip exposed to uninhibited liquid under the, same conditions.

Table l BIS-IMIDAZOLINEIMIDAZOLIDINE AND DI-IMIDAZOLIDINES l 2 3 4 Percent corrosion 25 5 p.p.m. p p m. p.p.m

Dimeracid. :1 5.7 42.7 do :2 1.1 4.1 17.5 d :1 8.7 13.8 Heptaldehyde. :2 5. 8 10. 1 22. 2 Benzaldehyde. 2 8. 9 6. 4 18. 1 d 1 1.2 2.4 50.0 TETA. Dimeracid. HCHO 1 5.0 10.1 TETA. Dimeracid Heptaldehydo. 2 0.9 9.2 25.7 TETA. Dimeraoid. Benzaldehyde. 1 5.4 5.2 27.1 TETA. Succiauie Heptaldehyde. :2 0.9 3.7 9.5

aci

TETA. do Benzaldehyda :2 1.6 18.3 37.9

Table II BIS-IMIDAZOLINE-IMINE AND DIIMINES 1 2 3 4 Percent corrosion D-D- P-p.m p.p.m

DETA. Dimeracid. None 2:1 DETA do ECHO 2:1:2 DETA. do Heptaldehyde. 2:1:1 DETA Suceinic None 2:1

Acid

2:1:2 Heptaldehydm 2:1:2 Benzaldehyde. 2:1:2

It will be evident from the foregoing that the aldehydemodified reaction products of the present invention are far more efficient as corrosion inhibitors in low concentrations than the amine-acid products made according to U. S. Patent 2,646,399. The reason for this is not known, since it would be expected that a free amino group would attach itself with greater vigor to a metal surfaceto provide a protective film. It may be, however, that true chemisorption is a rather slow process, and that when a chemical is rapidly adsorbed, layers are built up which are loosely bound and easily penetrated and removed by the physical action of liquids movingin the system.

In using my improved compositions for protecting oil Well tubing, casing, and other equipment which comes in contact with the corrosive oil-brine production, it has been found that excellent results may be obtained by injecting an appropriate quantity of a selected composition into a producing well so that it may mingle with the oil-brine mixture and come into contact with the casing, tubing, pumps, and other producing equipment. I may, for example, introduce the inhibiting composition into the top of the casing, thus causing it to flow down into the well and thence back through the tubing, etc. In general, I have found that this procedure suffices to inhibit corrosion throughout the entire system of production and collection, even including field tankage.

It is to be understood that the improved compositions of my invention are not limited to use alone and may be employed along with other agents commonly introduced into producing oil wells for breaking emulsions, limiting scale formation, etc. It is further evident that my invention is not restricted to the use of improved compositions for inhibiting corrosion in oil wells but may be employed to perform this function in the presence of corrosive brines of other origin.

. Having now described my invention, what is claimed is:

1. The method of protecting metal equipment which is subject to the corrosive action of oil well fluids which comprises adding to the fluids a minor quantity efiective to substantially inhibit the corrosion of the metal equipment of a compound having the generic formula (Fm-0H CHz.OHz RN N N NR in which one R is selected from the group consisting. of

in which R is selected from the group consisting of hydrogen atoms and hydrocarbon radicals, and the other R is selected from the group consisting of (4), (5), and (6), and Y is a hydrocarbon radical containing at least 2 carbon atoms, and thereafter causing the well fluids to come in contact with the metal to be protected.

2. The method according to claim 1 in which both Rs are (6), R is a hydrogen atom, andY is a dimerized linoleic acid residue.

5 3. The'method according to claim 1 in which both Rs are (6), R is -C H ,and Y is a dimerized linoleic acid residue.

4. The method according to claim 1 in which one R -is (2), the other R is (5), R is -C H and Y is a 5 dimerized linoleic acid residue.

5. The method according to claim 1 in which both Rs are (5), R is C H and Y is --C H 6. The method according to claim 1 in which both Rs are (4), R is a hydrogen atom, and Y is 'a dimerized 10 linoleic acid residue.

References Cited the file of this patent UNITED STATES PATENTS Blair et a1. Apr. 5,-1949 Blair et a1. Apr. 26, 1949 Gross et al. June 3, 1952 Hughes et a1. June 23, 1953 Hughes June 30, 1953 Hughes June 30, 1953 Hughes July 21, 1953 Hughes July 21, 1953 

1. THE METHOD OF PROTECTING METAL EQUIPMENT WHICH IS SUBJECT TO THE CORROSIVE ACTION OF OIL WELL FLUIDS WHICH COMPRISES ADDING TO THE FLUIDS A MINOR QUANTITY EFFECTIVE TO SUBSTANTIALLY INHIBIT THE CORROSION OF THE METAL EQUIPMENT OF A COMPOUND HAVING THE GENERIC FORMULA 